1. Field of the Invention
Methods and devices consistent with aspects of the present invention relate to an image forming apparatus, an image forming system including the same, and a printing method thereof, and more particularly, to an image forming apparatus with improved image quality, an image forming system including the same, and a printing method thereof.
2. Description of the Related Art
An image forming apparatus is an apparatus which prints image data output from a host device, such as a computer, a personal digital assistant (PDA) or the like, on a print medium, including a printer, a multifunction copier or the like.
Each of the pixels included in the image data has 8 bits for each of three RGB (red, green and blue) colors, that is, gray scale values between 0 and 255. However, in order to represent the pixel by dots, the 8-bit gray scale values are required to be converted into 1-bit (0 and 1) binary gray scale values. Such a series of conversion processes is referred to as “halftoning.”
In such a halftoning process, in some cases, different LPIs (Lines Per Inch) may be applied to different objects, such as a text, an image (a photograph, a picture, etc.), a graphic (a background of a text, a chart, etc.), included in the image data for improvement of image quality. In addition to the halftoning process, an emphasis process is performed for a boundary of a text included in the image data, through which a clearer image is obtained when the text is printed.
However, for example, where image data including a text (T) such as, “TRUM20” which is printed in a pink color, and a graphic (G) which is printed in gray, blue and pink colors in that order, and which is a background of the text (T), is subjected to halftoning and boundary emphasis processes, the image data may be printed as shown in FIG. 1. FIG. 1 shows a captured image obtained through a simulation of a print result.
As shown in FIG. 1, a defect in image quality such as sewing (which is called ‘stitch effect’) is produced in boundary portions (S) between the text (T) and the graphic (G) having different LPIs.
In addition, as can be seen in a region A of FIG. 1, if the text (a portion of “M”, “2” and a portion of “0”) and the graphic which is the background of the text have the same pink color, boundaries (B) of the text (the portion of “M”, “2” and the portion of “0”) are emphasized. This implies that the boundary of the text (T) is not properly detected since the text (T) has a different color from the graphic (G) which is in the background of the text (T) except in the region A. Conventional boundary detection algorithms provide low reliability of boundary detection since they detect boundaries based on change in gradation of color or gray (change in brightness).